If you don't know anything about Harry Partch, here's a great resource to check out.

From the website, about the Diamond Marimba:

"The Diamond Marimba, aside from being a prominent percussion instrument in many of Partch's works, is also a physical manifestation of one of his crucial theoretical concepts, the Tonality Diamond. The instrument contains all twelve of his primary tonalities, each laid out in a series of thirds. In total, the Diamond Marimba has 29 distinct pitches, each of which is a member of two or more tonalities."

You can read so much about Partch's theoretical concepts, his instruments, his music, and his life in "Genesis of a Music," a book first published in 1974.

Essentially, the ratio on each bar of the instrument corresponds to its tuning relative to the base pitch, G (392hz). The three rows below the 1/1 row sound below the base pitch, the lowest three notes sound an octave lower. The three rows above the 1/1 row sound above the base pitch, with the highest three notes sounding another octave higher.

It's easier to hear the relationships between notes when you can play more than one note at a time, and one of the unique techniques involved with playing this instrument involves sweeping down a diagonal row to hear an 'otonality' or 'utonality'. Feel free to use the "Click" setting to play individual notes, or the "Hover" setting to sweep through chords.